With recent economic development, the expansion of industrial scale and the concentration of big cities and factories have brought about a great increase in environmental contamination. As a result, water pollution has become a serious problem and drinking water is inevitablely purified through a water purifier prior to use. A water purifier is necessarily provided with a filter to filter raw water and the filter may be selected from a variety of water-purifying filters including non-woven fabric, activated carbon, activated carbon fiber (ACF), hollow fiber membrane, ion exchange resin and reverse osmosis filters, depending on the filtering method and steps.
As another conventionally used filter, a spiral wound type filter cartridge is suggested, which is disclosed in detail in Korean Patent No. 10-0477585, entitled “Method for preparing spiral wound type separation membrane module”.
The spiral wound type filter cartridge is generally moduled in a spiral wound shape using a flat-sheet type of ultrafiltration, nanofiltration or reverse osmosis membranes. In particular, ultrafiltration or reverse osmosis membranes utilize a partial filtration mode and are thus known to be highly resistant to contamination, compared to filtration modes of hollow fiber membranes, because a portion of introduced water containing concentrated contaminants is discharged to a concentrated-water discharge line. In addition, flat-sheet membranes used for spiral-wound type modules are characterized in that they are coated on a non-woven fabric and are thus more stable to operate at high pressures, as compared to hollow fiber membranes, and have a maximum efficient area for a constant volume. Meanwhile, nanofiltration and reverse osmosis membranes generally used as spiral wound type filter cartridges are capable of removing materials harmful to the human body, for example, waste such as iron or rust, microorganisms and heavy metal ions and are thus widely utilized not only in household water-purifier filter cartridges water but also in industrial water-purifier modules.
The spiral wound type filter cartridge comprises: a filter tube provided with a purified-water outlet on one side thereof and a plurality of water inlet holes in a longitudinal direction on the outside thereof and being in the form of a pipe; a filtering sheet repeatedly wound on the filter tube in the form of a roll, while being fixed on the one side of the filter tube under the condition that the one surface of a membrane sheet is closely adhered to a mesh sheet; and an adhesive sheet adhered to the filtering sheet such that the filtering sheet takes the circular housing appearance, while being wound on the filter tube, and is joined to a case provided with raw water inlet holes such that a purified water outlet is exposed to the outside.
When a purified-water inlet holes of filter tube is seen from the top in a longitudinal direction, the filtering sheet has a structure wherein both sides of the filtering sheet and bottom of the filter tube are closed by adhesion to take an envelope shape, the membrane sheet arranged at both sides has an inner structure wound in a spiral shape while including a mesh sheet for membrane providing a water channel, allowing purified water to flow to a filter tube, and the appearance thereof is wound to maintain the spiral wound state.
The spiral wound type filter cartridge is installed in an appliance such as a water purifier and carbon filters are provided in an inlet through which raw water enters and in an outlet through which purified water is discharged. Thus, the spiral wound type filter cartridge, together with the two carbon filters, sequentially filters the raw water.
The reason for providing carbon filters in the spiral wound type cartridge in pre- and post-treatment processes is that the spiral wound type filter cartridges can filter particulate materials, microorganisms or toxic minerals, but, of these, in particular, polyamide composite membranes have disadvantageously poor resistance to materials such as chlorine residues, and carbon filters are capable of efficiently removing contaminants such as organic chemicals or offensive odors.
Furthermore, the carbon filters are made of particulate activated carbon composed of materials such as wood, coconut or coal particles specifically heat-treated in order to provide several million fine holes, or of activated carbon fibers prepared by carbonizing fibers, and are used to remove various chemical contaminants. In particular, the carbon filters are effective in removing organic chemicals such as insecticides, weedicides or industrial waste and radon, chlorine and offensive odor thereof and are thus necessarily provided in a filtering area. However, the carbon filters disadvantageously cannot remove microorganisms or toxic minerals.
Accordingly, when spiral wound type filter cartridges or carbon filters are applied to water purifiers, the use of additional carbon filters is inevitably required for the process of pre- or post-treating the filter cartridges, thus disadvantageously incurring costs required for securing a sufficient area of the water purifiers and for installing the carbon filters.